1. Field of the Invention
The present invention relates to an engine unit for a vehicle that has a V-type engine and a throttle body assembly.
2. Description of Related Art
Various types of throttle body assemblies for V-type engines are known. For example, FIG. 12 illustrates a throttle body assembly 100 as disclosed in JP-A-2004-308536.
Throttle body assembly 100 includes a drum 102 attached to an input shaft 103. A wire 101 is wound around drum 102. Wire 101 is moved by operation of an acceleration grip (not shown) to rotate drum 102 and input shaft 103. An accelerator position sensor 116 is provided at one end of input shaft 103, which is also referred to as an accelerator position sensor (APS) shaft for this reason. The other end of input shaft 103 is connected to an output shaft 105 via a power transmission system 104. A gear 104a of power transmission system 104 is connected with a driving motor 120 via gears 121 and 122.
A base end of a first arm member 106 is fixed to a tip end of output shaft 105. One end of a first link 107 is attached to a tip end of first arm member 106 in a swingable manner. The other end of first link 107 is attached to a front arm portion 108a of a second arm member 108 in a swingable manner. Second arm member 108 rotates about a front valve shaft 109. A throttle valve 110 is attached to front valve shaft 109 in a front throttle portion 117. Front throttle portion 117 is opened and closed by throttle valve 110.
One end of a second link 111 is attached to a rear arm portion 108b of second arm member 108 in a swingable manner. The other end of second link 111 is attached to a tip end of a third arm member 112 in a swingable manner. A base end of third arm member 112 is fixed to a rear valve shaft 113. A throttle valve 114 is attached to rear valve shaft 113 in a rear throttle portion 118. Rear throttle portion 118 is opened and closed by throttle valve 114. A throttle position sensor 115 is attached to rear valve shaft 113 and detects a throttle opening angle.
When accelerator grip is operated, wire 101 moves and drum 102 and input shaft 103 rotate. The rotational amount of input shaft 103 is detected by accelerator position sensor 116 as an accelerator opening angle. Then, according to the detected accelerator opening angle, driving motor 120 is driven. The rotation of driving motor 120 is transmitted to front valve shaft 109 and rear valve shaft 113 via gears 121 and 122, power transmission system 104, output shaft 105, first arm member 106, first link 107, second arm member 108, second link 111, and third arm member 112. As a consequence, front valve shaft 109 and rear valve shaft 113 rotate, thereby opening and closing throttle valves 110 and 114.
As described in paragraph 50 of JP-A-2004-308536, input (APS) shaft 103 and output shaft 105 overlap with driving motor 120 in a vertical direction. Therefore, throttle body assembly 100 can be made compact and protrusion of throttle body assembly 100 from throttle portions 117 and 118 can be reduced.
As shown in FIG. 12, driving motor 120 is disposed between front throttle portion 117 and rear throttle portion 118. Therefore, compared with a case in which driving motor 120 is disposed in front of front throttle portion 117 or at the rear of rear throttle portion 118, a longitudinal length of throttle body assembly 100 is shortened. Nevertheless, since input (APS) shaft 103 and driving motor 120 are arranged one above the other in a vertical direction, it is difficult to make the height dimension of throttle body assembly 100 small enough. Accordingly, the use of throttle body assembly 100 makes it difficult to sufficiently reduce the size of the V-type engine.